The term “powder or the like” is used to mean any solid in a powder, granular, divided, or equivalent state that is light in weight, with a grain size of less than five millimeters (5 mm), that generates dust when handled, and that is suitable for mixing with a liquid. Below, the term “powder” is used more generically for “powder or the like”.
More precisely, in the device for mixing powder with a liquid as disclosed in DE 43 23 371, the first stirrer is immersed and, with the help of the first downward stream, generates a powder/liquid mixing interface at the surface of the liquid. Naturally, the top portion of the dispersion tube is outside the liquid.
Nevertheless, when powder is introduced into the dispersion tube, the powder reaches the surface of the liquid in order to be mixed therewith by being subjected to gravity, i.e. to its own weight. The lighter particles of the powder, i.e. the dust of the powder, remain in suspension in the emergent portion of the dispersion tube. In other words, this arrival of powder generates dust that is lighter than the powder and that disperses in the emergent portion of the dispersion tube. With continued use, this dust runs the risk of accumulating in the emergent portion of the dispersion tube and of leading to a malfunction of the dispersion tube, in particular by giving rise to a poor flow of powder, thereby leading to poor mixing, with possible formation of lumps of powder in the liquid. The dispersion tube then performs less well and may even become unusable. It is then necessary to dismantle it and clean it in order to return it to its initial operating state.